The terminology is a bit confusing between chromosome, chromatin, chromatid, hapolid, diploid, etc! I was looking online for some clear definitions, and I like this image.
1-Chromatid, 2-Centromere, 3-short arm, 4-long arm.
In Chem we have a test this week on gas laws, thermochemistry, and the quantum nature of electrons (acting as both particles and waves). It's kind of cool because atoms required a new understanding of physics--neither classic Newtonian physics nor Einstein's relativity could work here: "Quantum physics deals with situations where the usual picture of reality breaks down. Photons (discrete units of light) and other very small things have some behaviors that resemble classical particles like billiard balls and other behaviors that resemble classical waves like water waves." (From Wikipedia)
And in Physics, still struggling but it's getting better. We just finished a chapter on angular momentum and torque. Don't ask!